This project is focused on the study of the pathogenesis of HIV-associated malignancies and the development of novel therapies for these tumors based on this understanding. Much of the work on AIDS-related malignancies has focused on tumors associated with Kaposis sarcoma-associated herpesvirus (KSHV), also called human herpesvirus-8 (HHV-8). This virus is the cause of Kaposis sarcoma (KS), primary effusion lymphoma (PEL) and multicentric Castlemans disease (MCD). We have found that hypoxia can activate latent KSHV to undergo lytic replication and that several genes of KSHV are specifically upregulated by hypoxia. We had previously found that a gene of unknown function, ORF34, is specifically activated by hypoxia. ORF34 is part of a cluster of genes (ORF34 to 37). We have dissected the molecular structure of this gene cluster and its upregulation by hypoxia. One of these genes, ORF36, can phosphorylate ganciclovir, and activation of this gene by hypoxia may be able to be used to therapeutic benefit in KSHV-associated tumors, especially PEL. In addition, we have found that a KSHV-encoded thymidine kinase (ORF21) is upregulated in KSHV-infected cells exposed to hypoxia. This gene can phosphorylate zidovudine (AZT) to a form that is toxic for cells. We are currently exploring the interplay between hypoxia and other KSHV genes and in addition, the effects of hypoxia on KSHV-infected endothelial cells. We are also comparing the effects of hypoxia and the hypoxia-inducable factors (HIF-1 and HIF-2) on KSHV and cellular genes. Expanding on the observation that hypoxia upregulates ORF36 and ORF21, we have found that phosphorylation of ganciclovir and AZT is increased in PEL cells exposed to hypoxia and that clinically attainable concentrations of these drugs can kill the PEL cells. This approach could be used as a basis to treat either PEL (which develops in a hypoxic environment) or MCD (in which KSHV lytic genes are already activated). We are also exploring the biochemical mechanisms responsible for the upregulation of PTPRZ1, a gene important in the pathogenesis of glioma and renal cell carcinoma, by HIF-2 but not HIF-1, and have found that this selective upregulation by HIF-2 is due to a collaborative effect of HIF-2 and ELK1, an E26 transformation-specific (Ets) factor. We have also been conducting translational studies on patients with HIOV-associated malignancies. We have found differential expression of antibodies against KSHV latent and lytic proteins in patients with different KSHV-associated tumors. Finally, we are conducting laboratory studies to assess the levels of cytokines and other factors in patients on clinical trials for AIDS malignancies. We have identified a group of patients with KSHV infection but without MCD who have systemic inflammatory symptoms similar to that of MCD and who have high serum levels of KSHV-encoded viral interleukin-6 (vIL-6). This represents a new disease entity of KSHV interleukin-6 cytokine syndrome (KICS).